Modern semiconductor processing technology has advanced rapidly with increased transistor density, reduced chip area and improved transistor performance. In many cases, these advancements have come at the expense of increased leakage current. In the past, this leakage current has been small in comparison to the total chip power; however with advancing technologies, leakage current is becoming an increasingly larger percentage. Part of the reason for this increase in leakage current is that many newer technologies rely more on high-leakage semiconductor devices, which may have shorter channel lengths, thinner gate-oxide layers and/or lower threshold voltages than semiconductor devices of more conventional processing technologies.
This increasing leakage current is especially a concern for systems and devices that rely heavily on batteries, such as wireless communication devices. Such systems and devices may utilize a standby mode to reduce their power consumption. During standby mode, many active components of one or more voltage domains are powered down; however invalid data signals generated by circuitry of a voltage domain in the standby mode may result in an increased leakage current by other circuitry.
Level shifters are generally used to shift data signals from one voltage domain to another. One problem with some conventional level shifters is that invalid data signals may be generated during the standby mode causing an increase in leakage current in either the level-shifter circuitry itself and/or other circuitry. Thus, there are general needs for level shifters that provide firewall protection to help prevent the generation of invalid data signals and level shifters that help reduce leakage current in standby mode.